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SEOUL, South Korea (CNN) -- North Korean leader Kim Jong-il tapped his son to join the powerful National Defense Commission -- a move analysts say makes the latter the heir apparent, South Korean state media said. Kim Jong-il has appointed his youngest son and his brother-in-law to the National Defense Commission. "Kim Jong-un had been appointed to a low-level post, called 'instructor' at the National Defense Commission days before the first session of the 12th Supreme People's Assembly meeting was held," South Korea's Yonhap news agency reported, quoting a source. CNN was not able to independently confirm the report. The secretive North Korea shields its internal affairs from international scrutiny. And often, the only news coming the Communist nation is reported by its neighbor South Korea. The two countries have technically remained in a state of war since the Korean War ended in 1953, although relations have warmed somewhat in the last few years. The Korean conflict ended in a truce, but no formal peace treaty was ever signed. The 25-year-old picked for the North Korean defense commission is the youngest of Kim's three sons, Yonhap said. The move comes two weeks after Kim added his brother-in-law Jang Song Thaek to the military board. Analysts said Jang will serve as a caretaker for the successor, Yonhap said. Jang, who has been married to Kim's sister since 1972, is considered his right-hand man, according to Yonhap. Kim was reappointed this month as chairman of the military board in his first major public appearance since a reported stroke in August. His recent health problems and long absence from public functions prompted speculation on whether he was ready to groom an heir to the world's only communist dynasty.

North Korean leader Kim Jong-Il's son joins National Defense Commission .
South Korean media says move makes Kim Jong-un his father's heir apparent .
25-year-old is youngest of Kim's three sons .